1. Field of the Invention
The present invention relates to a delivery system, a transmission apparatus, and a delivery method, in particular, to a delivery system, a transmission apparatus, and a delivery method that deliver an audio signal that has been corrected according to an audio reproduction environment of a reception terminal.
2. Description of the Related Art
So far, a sound such as music has been digitally encoded and the resultant compressed audio signal has been provided to the user through the Internet. For example, the user can download an audio signal of his or her favorite music through the Internet, record the downloaded audio signal to a personal computer, reproduce the audio signal from the personal computer, and listen to his or her favorite music. When the user has transferred the audio signal to a portable reproduction terminal connected to the personal computer, he or she can listen to his or her favorite music even when he or she is out.
In this case, from a view point of copyright protection, as described in Japanese Patent Laid-Open Publication No. 2001-16109, hereinafter referred to as Patent Document 1, a technique that allows only a preregistered user to download his or her favorite audio signal has been proposed.
In addition, streaming delivery that transfers video data including moving image data, an audio signal, and auxiliary data through a network and reproduce them in real time has been performed. Since the streaming delivery allows the user to watch and listen to data without necessity of recording transmission data to a hard disk, it has advantages of reduction of listening waiting time, protection of illegal copy, and watching and listening of moving image data, audio signal, and so forth in real time.
In the stream delivery, for example, a moving image, an audio signal, and so forth as delivery materials are converted into streaming data and converted moving image data, audio signal, and so forth are uploaded to a delivery server. As streaming data of audio signal, a format including Windows Media Audio (extension: wma) that can be reproduced by Windows Media Player (registered trademark) and Real Audio (extension: ra) that can be reproduced by Real Player (registered trademark) is selected. Data updated to the delivery server are linked from web sites. Thus, when the user accesses a web site, clicks a link button for streaming content, and selects it, the delivery server starts delivery of streaming.
In recent years, so-called Internet radio delivery using streaming delivery has been performed. Internet radio is delivered to personal computers and wireless local area network (LAN), motor vehicle onboard terminals, and so forth through the Internet.
Audio reproduction environments of the reception terminal side that receives audio signal and so forth may be an environment using for example a headphone, an interior of a motor vehicle, a simple device associated with a personal computer, a so-called Hi-Fi audio device, and so forth. These terminals largely differ in acoustic effects.
However, so far, in radio broadcasts and cable television broadcasts using radio waves, a broadcast station has delivered the same data regardless of audio reproduction environments of reception terminals. In delivery using the Internet, although compression rates may have been selected according to capacities of communication lines, data having the same characteristics have been delivered regardless of audio reproduction environments of reception terminals.
Thus, as disclosed in Japanese Patent Laid-Open Publication No. 2003-111200, referred to as Patent Document 2, an acoustic processing device that corrects an audio signal according to the audio reproduction environment before a sound is output from a speaker (speakers) has been proposed.
The acoustic processing device of Patent Document 2 is a reclining chair type acoustic processing device having speakers disposed in the headrest portion and performs a sound image localization process that corrects an audio signal such that the user can hear sound generated behind his or her ears from a predetermined position, for example, in front of him or her.